Defining undernutrition for public health purposes in the United States.

Lack of consistency among definitions of undernutrition used for different public health purposes in the United States hinders an effective diagnosis of the problem and the design of interventions to prevent and treat undernutrition. No single-case definition of undernutrition is appropriate for all purposes. These purposes include surveillance of the prevalence of undernutrition in the population, epidemiological research on risk factors and consequences of undernutrition within population subgroups and communities, and screening, monitoring and evaluation of nutritional programs. We recommend that a cut-off of -2.0 SD (2.3 percentile) for weight-for-age, height-for-age, and weight-for-height on National Center for Health Statistics (NCHS) reference growth charts be used to estimate and monitor the prevalence of undernutrition in the United States, in accordance with guidelines of the World Health Organization. Epidemiological research on population-based risk factors for undernutrition and its functional consequences is required to identify the appropriate nutritional indicator and cut-off for screening and monitoring and evaluation of interventions.